diagno(i)se: tranny or Xcase?

[Iceman]

Hello all,

just checked out a buddy's TJ with AX15 and NP231 and it makes a thudding sound when in reverse, NOT when going forward. You can see the Xcase shudder and when you put your hand on the Xcase you can feel it too (with Xcase in N ...duh ... and tranny in reverse)
If you put it in neutral and the tranny in reverse -> same thing. It almost sounds like something is misaligned. Could it be the reverse synchro inside the tranny, just transferring it into the Xcase or could it be the input shaft into the Xcase or a fork inside the Xcase or ...

it doesn't seem to be related to torque input, since even in 4low it won't make the noise in forward, just in reverse

any help and info is welcome, before we start tearing into the stuff

[mrblaine]

Originally posted by Iceman
Hello all,

just checked out a buddy's TJ with AX15 and NP231 and it makes a thudding sound when in reverse, NOT when going forward. You can see the Xcase shudder and when you put your hand on the Xcase you can feel it too (with Xcase in N ...duh ... and tranny in reverse)
If you put it in neutral and the tranny in reverse -> same thing. It almost sounds like something is misaligned. Could it be the reverse synchro inside the tranny, just transferring it into the Xcase or could it be the input shaft into the Xcase or a fork inside the Xcase or ...

it doesn't seem to be related to torque input, since even in 4low it won't make the noise in forward, just in reverse

any help and info is welcome, before we start tearing into the stuff

Remove the rear driveshaft and do it again to make sure it's not something in the rear axle transferring up the driveshaft.

If it still is isolated to the t-case, I'd guess it's been run low on fluid, overheated and the chain is whacked on the sprockets.

[Iceman]

but how does that relate to the fact that it only does it in reverse though, Blaine? If it would be actually in the Xcase you would say it also happens in forward gears, especially in 4hi and 4lo.

The more I think about it, the more it seems to me that something went wrong with the reverse synchro or shift fork ... make sense?

[mrblaine]

Originally posted by Iceman
but how does that relate to the fact that it only does it in reverse though, Blaine? If it would be actually in the Xcase you would say it also happens in forward gears, especially in 4hi and 4lo.

The more I think about it, the more it seems to me that something went wrong with the reverse synchro or shift fork ... make sense?

You could have some teeth on the ring gear pushed over to where they clunk on reverse rotation and not on forward rotation.

If the teeth on the sprocket are worn in one direction it will let the chain travel smoothly that direction and hang up going the other way.

Pure speculation

[Iceman]

Originally posted by mrblaine
You could have some teeth on the ring gear pushed over to where they clunk on reverse rotation and not on forward rotation.

If the teeth on the sprocket are worn in one direction it will let the chain travel smoothly that direction and hang up going the other way.

Pure speculation

okay, that makes sense ... we'll check it out